Heat exchangers are well know devices that are used to reduce or increase the temperature of a fluid or gas being directed therethrough. Most commonly, heat exchangers are used to reduce the temperature of a fluid being passed through it so that the cooled fluid or gas can be used for another purpose. Heat exchangers can be used in conjunction with used with internal combustion engines, for example, to reduce the temperature of an exhaust gas stream from an exhaust gas recirculation (EGR) system before being directed into the engine's intake system for combustion, and to reduce the temperature of a pressurized intake air charge in a turbocharged or supercharged system before being directed into the engine's intake system for combination.
Heat exchanger's used for these purposes can make use of air or a liquid as the needed cooling medium, can be configured having a single pass or multi-pass arrangement of passages through which the entering hot side fluid or gas and entering cold side fluid undergo heat exchange. Regardless of the particular heat exchanger construction, all heat exchangers are designed to provide a desired degree of performance within a defined set or operating parameters. These operating parameters typically include the entering hot side fluid or gas temperature and pressure, and the entering cold side fluid temperature and pressure.
The service life of a heat exchanger is greatly influenced by the operating parameters and conditions that it is subjected to. Perhaps the most critical heat exchanger operating parameter is that of the entering hot side fluid or gas temperature. It is well know for heat exchangers to prematurely fail in service when they have been placed in a service where the temperature of the entering hot side fluid exceeds the design temperature. This type of heat exchanger failure can occur over a period of time or can occur instantly, depending on the extent to which the temperature exceeds the design temperature, and depending on whether exposure to the temperature increase is something that is cyclic or steady over time.
Since there is typically no way of monitoring or determining the temperature of an entering fluid or gas stream directed into a heat exchanger placed into use with an internal combustion engine, a user often does not know what caused the heat exchanger to fail. Therefore, once a heat exchanger does fail, the user often goes back to the manufacturer to make a warranty claim. Because it is often difficult for a manufacturer to determine the exact cause of the heat exchanger failure, for the purpose of maintaining customer relations, many manufacturers honor the claim. This occurs despite the fact that the manufacturer may suspect that the heat exchanger has been misused or abused because it is difficult if not impossible to prove.
Attempts have been made to address this problem in the form of using inexpensive instrumentation to monitor or determined the temperature of the incoming hot side fluid stream. Such instrumentation have been configured to monitor the surface temperature of a portion of the heat exchanger or portion of the hot side fluid inlet. However, these external measurement devices do not provide an accurate indication of the temperature seen within the heat exchanger and do not provide an indication of spike or sudden temperature increases, thus have not proven to be that effective.
It is, therefore, desirable that a device be configured that is capable of providing an indication of the operating temperature within a heat exchanger to determine whether the heat exchanger has been subjected to an operating temperature beyond its design temperature. It is further desired that the device be configured in such a manner as to provide a fool proof means of indicating the design temperature has been exceeded to enable the heat exchanger manufacture to know with certainty that the heat exchanger has been subjected to an operating temperature greater than the design temperature.